By Damien McElroy in Aleppo province and Magdy Samaan in CairoInsurgents from the Free Syrian Army (FSA) claimed to have come under direct assault from two Russian-made MiGs in the southern part of the conurbation of at least 2 million people. "They were attacking us," one rebel fighter told The Daily Telegraph.
Aleppo is Syria's commercial capital and the FSA are now focusing their efforts on its capture. If they succeed, this would be a crucial setback for President Bashar al-Assad's regime.
While the security forces have routinely used helicopter gunships, they had never previoulsy dispatched fixed wing aircraft for ground attack missions. The intervention by the MiGs apparently came in response to rebels seizing part of Aleppo's old city, a United Nations World Heritage Site.
If the regime continues to mount these air strikes, this could reawaken the debate over Western intervention to reduce the bloodshed by imposing a "no-fly" zone. The decision by Col Mummar Gaddafi to deploy jets against the Libyan uprising was a decisive factor in the West's decision to topple him, which began when the world's leading powers effectively grounded his air force.
The Syrian authorities have been fighting back since suffering severe losses in the confusion following the assassination of four senior commanders in Damascus last week. Their attempts to clear rebellious suburbs of the capital continued yesterday.
Activists said they were dropping leaflets from helicopters calling on the opposition to surrender. "The weapon you are carrying has become a burden on you, and there is no hope for you to survive unless you drop your weapon," read the leaflets. "The moment of truth has come."
But in Aleppo, Syria's industrial hub, the regime faces an opposition which, although out-gunned, has a carefully worked out strategy. The FSA is flooding streets with fighters, attacking the army's positions, but swiftly withdrawing when the response becomes too fierce.
That tactic seemed to have worked, placing Mr Assad's forces on the defensive in all quarters of the city, including the old citadel, where winding alleys are too narrow for tanks.
"The regime will have to level the ancient Aleppo to the ground," said Ayman al-Sulman, an FSA volunteer "The whole world would see this and Bashar al-Assad will be an enemy of all human history."
The FSA opened its attack on Aleppo by pouring in recruits from villages around the city, dividing it into four quarters and controlling its fighters via radio and the mobile phone networks. Rebels described hand-to-hand combat against the regime's "Shabiha" militia. "The Shabiha were attacking us as soon as we arrived," said Ahmed, a 17-year-old orphan whose uniform was a blue shell-suit. He joined the 40 men of the FSA's Abdul-Hamid Battalion in the suburb of Salahaddin.
It was the first time that he had used a gun, he said. The weapon's recoil had left a purple mark on his forearm. "We fired a lot and they pulled back, but we stayed where we were," he said. "There were only a few people still at home in street. Later there were mortars fired at us but not too many."
Abu Marwan, 57, a rebel scout, said the army had withdrawn its checkpoints from Salahaddin and at least two other areas, Haydiriyah and Masakin Hanano.
"For now we are winning," he said. "I could move my car through Aleppo to the points where we have fighters quite easily. The danger is in the air. The government is firing into anywhere it does not have its men."
The regime's forces were also trying to suppress a mutiny in Aleppo's main prison, according to activists. The inmates, many of them captured during the uprising, were holding three army officers as hostages, the reports said.
"What happened was a rebellion and not an attempt to escape," said Farouk al-Ahmed, an opposition activist in Aleppo. "Security forces responded by opening fire and tear gas on the prisoners, and 10 people were martyred."
He said the FSA were warning people to take shelter in basements because of helicopter attacks, but he could not confirm the use of fighter jets.